Europium oxide as a perfect electron spin filter

Essential to the emergence of spin-based electronics is a source of highly polarized electron spins. Conventional ferromagnets have at best a spin polarization P-50%. Europium monoxide is a novel material capable of generating a highly spin-polarized current when used as a tunnel barrier. EuO is both a Heisenberg ferromagnet (Tc=69 K) and a semiconductor. Exchange splitting of the conduction band creates different tunnel barrier heights for spin-up and spin-down electrons, thus filtering the spins during tunneling. High-quality EuO films at the monolayer level is necessary for efficient spin-filtering. Because non-ferromagnetic, insulating Eu20 forms more readily, growth of an ultra-thin, high-quality film is quite challenging, which restricted previous studies of EuO to bulk form. EuO films were grown by reactive thermal evaporation, and various thin film characterization techniques were employed to determine the structural, optical, and magnetic properties, even on the thickness scale needed for tunneling (<3 nm). The film properties closely matched those of bulk EuO, though the Tc for ultra-thin films was found to be reduced from bulk value, in agreement with theoretical prediction.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Materials Science and Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2007

Author dc:creator

• Santos, Tiffany S. (Tiffany Suzanne), 1980-

Advisor dc:contributor.advisor

• Jagadeesh Moodera.

• Materials Science and Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/39538
• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Identifier URI

http://dspace.mit.edu/handle/1721.1/39538

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/39538